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Questions and Answers
What occurs when DO2 dips below VO2?
What occurs when DO2 dips below VO2?
What is a consequence of prolonged decreased DO2?
What is a consequence of prolonged decreased DO2?
During the compensatory stage of shock, which of the following is usually observed?
During the compensatory stage of shock, which of the following is usually observed?
Which symptom is indicative of decompensatory shock?
Which symptom is indicative of decompensatory shock?
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What may result from cellular edema in situations of decompensatory shock?
What may result from cellular edema in situations of decompensatory shock?
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What is the primary indicator of shock related to oxygen delivery?
What is the primary indicator of shock related to oxygen delivery?
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Which equation represents the oxygen delivery (DO2)?
Which equation represents the oxygen delivery (DO2)?
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Which component is NOT part of the oxygen content (CaO2) equation?
Which component is NOT part of the oxygen content (CaO2) equation?
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What physiological state can occur due to decreased oxygen delivery to tissues?
What physiological state can occur due to decreased oxygen delivery to tissues?
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What characterizes decompensatory shock?
What characterizes decompensatory shock?
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How do tissues respond to decreased ability to utilize delivered oxygen?
How do tissues respond to decreased ability to utilize delivered oxygen?
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What is the role of hemoglobin in oxygen delivery?
What is the role of hemoglobin in oxygen delivery?
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Which factor would most likely lead to decreased oxygen delivery to tissues?
Which factor would most likely lead to decreased oxygen delivery to tissues?
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What is the primary function of capillaries in the oxygen delivery process?
What is the primary function of capillaries in the oxygen delivery process?
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Which factor is NOT typically associated with increased tissue oxygen demand?
Which factor is NOT typically associated with increased tissue oxygen demand?
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What mechanism of cellular respiration does NOT require oxygen?
What mechanism of cellular respiration does NOT require oxygen?
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What is the main consequence of hypovolemia on oxygen delivery?
What is the main consequence of hypovolemia on oxygen delivery?
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Which of the following conditions is considered relatively rare concerning oxygen utilization?
Which of the following conditions is considered relatively rare concerning oxygen utilization?
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What role does smooth muscle play in the arterioles?
What role does smooth muscle play in the arterioles?
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How does an increased surface area in capillaries impact oxygen diffusion?
How does an increased surface area in capillaries impact oxygen diffusion?
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What is a key characteristic of aerobic respiration compared to anaerobic respiration?
What is a key characteristic of aerobic respiration compared to anaerobic respiration?
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What is produced from pyruvate during anaerobic metabolism?
What is produced from pyruvate during anaerobic metabolism?
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What effect does lactic acidosis have on blood pH?
What effect does lactic acidosis have on blood pH?
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Under normal conditions, what percentage of oxygen is extracted by tissues from blood?
Under normal conditions, what percentage of oxygen is extracted by tissues from blood?
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Which parameter can increase up to 60-70% to meet oxygen demand?
Which parameter can increase up to 60-70% to meet oxygen demand?
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What physiological response occurs if delivery of oxygen (DO2) decreases to near or below tissue oxygen demand (VO2)?
What physiological response occurs if delivery of oxygen (DO2) decreases to near or below tissue oxygen demand (VO2)?
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Which condition is difficult to change quickly without assistance?
Which condition is difficult to change quickly without assistance?
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What measurement can indicate lactic acidosis in the blood?
What measurement can indicate lactic acidosis in the blood?
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When blood bypasses tissues, what parameter can be falsely increased?
When blood bypasses tissues, what parameter can be falsely increased?
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What is the normal saturation range of hemoglobin (Hb)?
What is the normal saturation range of hemoglobin (Hb)?
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How is oxygen content measured in terms of hemoglobin?
How is oxygen content measured in terms of hemoglobin?
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What does the packed cell volume (PCV) equal in relation to hemoglobin ([Hb])?
What does the packed cell volume (PCV) equal in relation to hemoglobin ([Hb])?
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How is cardiac output determined?
How is cardiac output determined?
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Which factor is NOT mentioned as affecting cardiac output?
Which factor is NOT mentioned as affecting cardiac output?
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What is the effect of decreased oxygen delivery due to lung disease?
What is the effect of decreased oxygen delivery due to lung disease?
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How much oxygen is dissolved in blood per given amount of oxygen partial pressure (PaO2)?
How much oxygen is dissolved in blood per given amount of oxygen partial pressure (PaO2)?
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Which of the following is a factor that impacts oxygen delivery?
Which of the following is a factor that impacts oxygen delivery?
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Study Notes
Introduction to Shock
- Shock is characterized by decreased oxygen delivery to tissues and reduced tissue utilization of delivered oxygen.
- Objectives for understanding shock include: the oxygen delivery equation, how disruptions in oxygen delivery components lead to shock, physiologic responses to shock, compensatory and decompensatory shock, and blood lactate as an indicator of oxygen delivery.
Oxygen Delivery (DO2)
- Oxygen delivery, denoted as DO2, is calculated as Cardiac Output (Q) multiplied by arterial oxygen content (CaO2).
- Cardiac output is a product of heart rate (HR) and stroke volume (SV).
- Arterial oxygen content (CaO2) is determined by hemoglobin (Hb), oxygen saturation (SaO2), and dissolved oxygen in the blood (PaO2).
Oxygen Content (CaO2)
- CaO2 is a measure of the total oxygen dissolved in the blood and carried by hemoglobin.
- The formula for CaO2 is 1.34 x [Hb] x SaO2 + 0.003 x PaO2.
- Factors influencing oxygen content include hemoglobin concentration, oxygen saturation, and partial pressure of oxygen in the blood.
- Packed cell volume (PCV) is ~1/3 of hemoglobin.
Oxygen Binding Curve
- Oxygen saturation (SaO2) and partial pressure of oxygen (PaO2) are related.
- The relationship is illustrated by the oxygen-hemoglobin dissociation curve, showing the percentage of hemoglobin saturated with oxygen across various oxygen pressures.
Decreased Oxygen Delivery
- Factors affecting oxygen delivery include insufficient oxygen in the blood (low oxygen content, lung disease), inadequate tools for oxygen delivery (cardiovascular issues, hypovolemia), and tissue oxygen use.
- Tissue factors impacting oxygen use include high metabolic rates, increases in body temperature, intense exercise, and cyanide poisoning.
Oxygen Delivery to Cells
- Oxygen travels through the circulatory system from the heart to the aorta, then to arterioles, and finally to capillaries (where gas exchange occurs).
- Capillaries provide a large surface area for efficient oxygen diffusion.
Cellular Respiration
- Cellular respiration involves both aerobic and anaerobic processes.
- Anaerobic respiration, less efficient, occurs when oxygen is limited, producing lactate as a byproduct.
- Aerobic respiration, more efficient, uses oxygen and occurs in the mitochondria.
What Happens with Low Tissue Oxygenation?
- Low tissue oxygenation causes a shift to anaerobic metabolism.
- Anaerobic metabolism produces lactate and metabolic acidosis.
- Decreased perfusion and oxygen content lead to reduced oxygen supply.
Lactate
- Lactate is produced from anaerobic metabolism.
- Increased lactate signifies low tissue oxygen levels.
- Blood lactate measurement can help assess the severity of shock. Values can be measured by using a clinical device or testing the blood.
How to Estimate Oxygen Demand (VO2)
- Oxygen extraction ratio (CaO2-CvO2)/CaO2) is a method for approximating tissue oxygen demand.
- This ratio shows how much oxygen tissues extract from the blood.
- Normally, this ratio is between 20-30%.
- Elevated values could indicate an increase in tissue demand for oxygen.
Aerobic Respiration & Compensation
- Aerobic respiration (with sufficient oxygen) is important in compensation of lowered oxygen delivery as the body tries to maintain blood oxygen.
- Compensation includes increased heart rate and output, increased stroke volume and oxygen extraction ratio. Increased heart rate and output.
- As oxygen delivery declines, compensation eventually fails at which point decreased oxygen delivery transitions into decompensatory shock.
Decompensatory Shock
- Decompensatory shock occurs when oxygen delivery (DO2) falls below metabolic oxygen need (VO2).
- Without sufficient oxygen, tissues switch to anaerobic metabolism leading to lactate build-up, decreased ATP production and cellular gradients.
- Continued low oxygen delivery can lead to organ dysfunction, necrosis, and other serious outcomes.
Shock: General Physical Examination
- Compensatory shock typically presents with tachycardia, tachypnea, and normal or elevated blood pressure.
- Decompensatory shock often shows bradycardia, tachypnea, grey or purple mucous membranes, and hypotension.
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Description
This quiz explores the critical concepts related to shock, including its physiological responses, the oxygen delivery equation, and how various components impact oxygen supply to tissues. Additionally, it delves into the measures of oxygen content in the blood and their significance in understanding shock.